EditorialGuy - 2:53 pm on Jul 7, 2013 (gmt 0)
I guess because of Panda/Penguin, Google can say "we give up, commercial results are now paid only" rather than revert back to pre-Panda/Penguin when there was more variety in commercial searches because there were more independents in the top 10s than these "savvy" companies representing themselves several times over via tricks / churn & burn sites + crowd-hosted (whatever you call it) Amazon/eBay blocks of results.
I can remember a time when eBay (to use one of your examples) was a lot more dominant in the SERPs than it is now. Ditto for thin affiliate sites, which once were nearly all you could find if you searched on, say, the Hotel Whatever in Touristville.
Another thing to keep in mind is that Google Search is an index, not a directory, and the purpose of a spider-based search engine is to organize and rank content on pages. It may be true that a megasite like Amazon benefits from its sheer size and number of inbound links, but Amazon product pages do tend to have user reviews that add value to e-commerce listings. Since Google Search is more about identifying content on a page than figuring out who has the best price, the best customer service, or the lowest shipping fees, Amazon's "added value" in terms of content is going to help Amazon rank higher than independent sites that lack such content.
So how can Google clean up its commercial SERPs? One approach might be to:
1) Make it more difficult to rank for purely transactional pages.
2) Make it easier to rank for informational pages (even in the context of transactional queries).
In other words, in a search on "unicorn cheeses," the algorithm would tend to favor pages with intrinsically-useful content about unicorn cheeses, and the e-commerce vendors who'd rank best would be those who made the effort to be authoritative sources of advice for buyers and fanciers of unicorn cheeses. Google's SERPs would improve, and niche e-commerce sites run by product experts--or by business people who were willing to invest in "added value" content--would stand a better chance of competing with black hats and general-interest megasites.